34/4-5

General

Wildcat well 34/4-5 was drilled on the Mort Horst in the Northeastern part of the block. The purpose of the well was to test the Zeta structure for hydrocarbons and to test the stratigraphy below the Base Cretaceous Unconformity. The well encountered hydrocarbons in the Cook Formation and in the Statfjord Formation.

Operations and results

The well was spudded with the semi-submersible installation Treasure Saga on November 13 1983 and drilled to TD at 3917 m in Early - Middle Triassic sediments of the Lunde Formation. The well was drilled with seawater and bentonite down to 533 m, with bentonite/gypsum mud from 533 m to 1113 m, with gypsum/polymer mud from 1113 m to 2025 m, with gypsum/lignosulfonate (Unical) mud from 2025 m to 3200 m, and with lignosulfonate from 3200 m to TD.

Due to severe boulder problems in the 26" hole section, the well had to be re-spudded three times before the 20" casing could be run and cemented. The 20" casing had to be worked and washed down to the planned depth. This action most likely buckled or partly collapsed the 20" casing. It took approximately 5 days to drill/mill out the bottom section of the 20" casing. Circulation was lost at 2026 m when drilling the 17 1/2" hole. Due to the lost circulation, the 13 3/8" casing had to be set at 2011 m. The 12 1/4" section had to be plugged back from 3106 m to 3005 m due to severe hole deviation problems. The maximum hole angle was 8.75°. Re-drilling this hole section and deepening it down to 3200 m the hole angle varied between 3° and 4°. The 9 5/8" casing was set at 3195 m. The 8 1/2" hole section was drilled down to 3424 m, where the first core was cut. The core recovered shale, and it was decided to drill ahead. The hole was drilled down to 3470 m, where a new drill break occurred. While circulating bottoms up for samples a kick was taken. A total of 43 bbls were gained before closing in the well